p PatchFirst

CVE-2026-52870

CVE-2026-52870 · MCP Python SDK: Experimental task handlers allow any client to access and cancel other clients' tasks

This page contains facts from public vulnerability sources. Check the original advisory before updating.

The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). From 1.23.0 until 1.27.2, default handlers installed by server.experimental.enable_tasks() for tasks/list, tasks/get, tasks/result, and tasks/cancel operate only on task identifiers without recording the session that created each task, allowing any connected client to enumerate, read results from, consume messages for, or cancel other clients' tasks. This issue is fixed in version 1.27.2.

CVSS 7.6 · High · EPSS 0.4% · Fix available

Published
Updated

Stack: python

Affected products and versions

  • python-sdk

    Versions
    • >= 1.23.0, < 1.27.2: Affected

    No fix published

  • mcp PyPI

    Versions
    • 1.23.0
    • 1.23.1
    • 1.23.2
    • 1.23.3
    • 1.24.0
    • 1.25.0
    • 1.26.0
    • 1.27.0
    • 1.27.1
    Affected ranges
    • ECOSYSTEM: ≥ 1.23.0, < 1.27.2

    Update to 1.27.2

Original sources

Check your server →